PROJECT SUMMARY With 37 million people living with HIV/AIDS (including 1.2 million in the US), and 1.1 million AIDS-related deaths in 2015, HIV/AIDS remains a formidable global epidemic (UNAIDS, CDC). Modern HIV therapy combines drugs from different classes to form ?cocktail? therapies that have transformed HIV into a manageable chronic infection for many individuals. Despite the effectiveness of these drugs, side effects and drug resistance remain serious concerns for these life-long therapies. Thus, there is an enduring need for novel HIV inhibitors with new mechanisms of action and stronger barriers to resistance. Furthermore, it is recognized that lack of patient compliance is a major factor leading to treatment failure. For this reason, HIV specialists are excited by the prospect of long-acting therapies, and a cocktail of such therapies would provide a revolutionary new treatment option for many HIV patients. Navigen is a small pharmaceutical company targeting infectious diseases through an innovative discovery and design process. We have identified a novel HIV entry inhibitor, cholesterol-PIE12-trimer (CPT31), that is a protease-resistant D-peptide (peptide made from D-amino acids) that targets HIV's conserved entry machinery. With highly potent activity against all major HIV subtypes and designed barriers to resistance, our anti-HIV D- peptide overcomes the current limitations of the entry inhibitor treatment class. In addition, CPT31 is ideal for pre-exposure prophylaxis (PrEP) since it blocks the first stage of the viral lifecycle prior to infection of target cells. CPT31 is currently in late preclinical development at Navigen. CPT31's uniquely conserved target, superior resistance profile, high potency, protease resistance, and favorable pharmacokinetic (PK) and physicochemical properties make it an ideal candidate for extended- release depot formulation. Via a one-year R56 bridge grant, we have worked with an industry-leading formulation group at Oakwood Labs to demonstrate the feasibility of developing a long-acting formulation of CPT31 (CPT31-LA) suitable for once-monthly injection. Optimization of CPT31-LA is currently underway. In this three-year grant application, using optimized CPT31-LA, we will perform 1) required activities for scale-up and manufacturing in preparation for clinical trials, 2) rat and non-human primate (NHP) PK studies, 3) rat toxicology studies, and 4) NHP prevention (PrEP) and therapeutic efficacy studies. These studies will greatly facilitate development partnerships to advance CPT31-LA through IND filing and clinical trials. Once-monthly CPT31-LA will provide a potentially transformative new option for the prevention and treatment of HIV.